Executives at General Motors defended the 2012 ChevroletVolt as safe, even as the National Highway Traffic Safety Association began a formal safety investigation into the vehicle's safety.

As the NHTSA conducts its investigation, Chevrolet will provide any current owner with a loaner vehicle until the agency concludes its investigation, the automaker said. Those who want a loaner can contact their Volt advisor to arrange for a trade-in.

"A vehicle loan program of this nature is well beyond the norm for a preliminary investigation, and it underlines our commitment to the vehicle and its owners," Mark Reuss, president of GM North America, said in a statement. "These steps are the right ones to take regardless of any immediate impact on our operations."

The Chevrolet Volt has been perhaps the most highly publicized effort by an American carmaker to develop a hybrid vehicle. The Volt's appeal, in hands-on tests, is that the car can go a rated 35 miles on electricity alone before shifting to a gas-powered electric generator that can add hundreds of miles to its range. The Volt uses lithium-ion batteries to store a charge. It qualifies as a low-emissions vehicle that will be able to drive in California's HOV lanes, even with just the driver in the car.